From: Andrew Morton <akpm@linux-foundation.org>
To: Vasiliy Kulikov <segoon@openwall.com>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>,
kernel-janitors@vger.kernel.org,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] fs: select: fix information leak to userspace
Date: Sun, 14 Nov 2010 18:06:43 -0800 [thread overview]
Message-ID: <20101114180643.593d19ac.akpm@linux-foundation.org> (raw)
In-Reply-To: <20101114092533.GB5323@albatros>
On Sun, 14 Nov 2010 12:25:33 +0300 Vasiliy Kulikov <segoon@openwall.com> wrote:
> On some architectures __kernel_suseconds_t is int. On these archs
> struct timeval has padding bytes at the end. This struct is copied to
> userspace with these padding bytes uninitialized. This leads to leaking
> of contents of kernel stack memory.
>
> Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
> ---
> Patch v1 used memset(), it was waste of cycles on almost all archs.
>
> Compile tested.
>
> fs/select.c | 7 ++++---
> 1 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/fs/select.c b/fs/select.c
> index b7b10aa..43d4805 100644
> --- a/fs/select.c
> +++ b/fs/select.c
> @@ -288,7 +288,6 @@ static int poll_select_copy_remaining(struct timespec *end_time, void __user *p,
> int timeval, int ret)
> {
> struct timespec rts;
> - struct timeval rtv;
>
> if (!p)
> return ret;
> @@ -306,8 +305,10 @@ static int poll_select_copy_remaining(struct timespec *end_time, void __user *p,
> rts.tv_sec = rts.tv_nsec = 0;
>
> if (timeval) {
> - rtv.tv_sec = rts.tv_sec;
> - rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC;
> + struct timeval rtv = {
> + .tv_sec = rts.tv_sec,
> + .tv_usec = rts.tv_nsec / NSEC_PER_USEC
> + };
>
> if (!copy_to_user(p, &rtv, sizeof(rtv)))
> return ret;
Please check the assembly code - this will still leave four bytes of
uninitalised stack data in 'rtv', surely.
next prev parent reply other threads:[~2010-11-15 2:06 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-10 20:38 [PATCH] fs: select: fix information leak to userspace Vasiliy Kulikov
2010-11-12 20:08 ` Andrew Morton
2010-11-13 21:38 ` Andreas Dilger
2010-11-14 9:25 ` [PATCH v2] " Vasiliy Kulikov
2010-11-15 2:06 ` Andrew Morton [this message]
2010-11-15 19:12 ` Eric Dumazet
2010-11-16 11:19 ` Boaz Harrosh
2010-11-22 23:50 ` Andrew Morton
2010-11-23 0:20 ` Eric Dumazet
2010-11-23 0:32 ` Andrew Morton
2010-11-23 5:12 ` Dan Carpenter
2010-11-23 6:59 ` Eric Dumazet
2010-11-23 14:01 ` Américo Wang
2010-11-23 14:45 ` walter harms
2010-11-23 15:23 ` Américo Wang
2010-11-23 18:02 ` Andreas Dilger
2010-11-23 20:18 ` Andrew Morton
2010-11-23 20:22 ` David Miller
2010-11-24 0:24 ` Andreas Dilger
2010-11-24 16:06 ` walter harms
2010-11-24 10:44 ` Pádraig Brady
2010-11-24 11:05 ` Américo Wang
2010-11-24 11:46 ` Pádraig Brady
2010-11-24 12:32 ` Américo Wang
2010-12-15 9:49 ` Al Viro
2010-12-15 20:30 ` Andreas Dilger
2010-12-15 20:33 ` Julia Lawall
2010-12-15 20:52 ` Eric Dumazet
2010-12-15 22:19 ` Andreas Dilger
2010-12-16 9:39 ` Boaz Harrosh
2010-11-24 17:54 ` Valdis.Kletnieks
2010-11-16 18:45 ` Vasiliy Kulikov
2010-11-15 2:05 ` [PATCH] " Andrew Morton
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